Electrode material for electrolytic hydrogen generation

ABSTRACT

Some examples of a method for manufacturing an electrode material for electrolytic hydrogen generation are described. Tungsten salt and nickel salt are mixed in a determined molar ratio on a carbon support by effectively controlling synthesis temperature and composition. Water and adsorbed oxygen, produced by mixing the tungsten salt and nickel salt are removed. Then, methane gas is flowed over the mixture resulting in the electrode material. The electrode material is suitable for use as a catalyst in electrolytic hydrogen generation processes, for example, at an industrial scale, to produce large quantities of hydrogen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityto U.S. patent application Ser. No. 15/147,252, filed May 5, 2016, whichclaims the benefit of U.S. Provisional Application Ser. No. 62/190,574,filed on Jul. 9, 2015, the contents of which are hereby incorporated byreference.

TECHNICAL FIELD

This disclosure relates to hydrogen generation, for example, byelectrolysis.

BACKGROUND

Hydrogen can be produced by several techniques including, for example,steam reforming from hydrocarbons, electrolysis, and thermolysis.Electrolysis of water is the decomposition of water (H₂O) into oxygen(O₂) and hydrogen (H₂) gases due to an electric current being passedthrough the water. Hydrogen can be produced throughphotovoltaic/electrolysis systems, alkaline electrolysis, acidic mediumelectrolysis, methanol oxidation, borohydride solution, or othertechniques. Catalysts are often used in electrolytic systems tofacilitate hydrogen production. Organic pigments, for example, can beused as catalysts for the release of hydrogen from a hydrogen-richborohydride solution. Other examples of catalysts include Platinum (Pt).Because industrial quantities of hydrogen can be produced moreaffordably using hydrocarbons, electrolysis is not frequently used inindustrial production of hydrogen.

SUMMARY

This disclosure describes electrolytic hydrogen generation and anelectrode material for electrolytic hydrogen generation, for example,from brine water.

Some aspect of the subject matter described here can be implemented as amethod. A first quantity of tungsten (W) salt and a second quantity ofNickel (Ni) salt are mixed on a carbon support. Methane gas is flowedover the mixture of the first quantity and the second quantity to formtungsten-nickel carbides (W—Ni—C) on the carbon support. For example,the methane gas is flowed at high temperature. The resulting product wasan electrode material suitable for use in electrolytic hydrogengeneration, for example, on an industrial scale, to produce largequantities of hydrogen.

This, and other aspects, can include one or more of the followingfeatures. The tungsten salt can be dissolved in isopropanol. The nickelsalt can be on a carbon support. Water and oxygen can be removed and themethane gas can be flowed over the mixture after removing the water andoxygen. The carbon support can be pre-treated before mixing the firstquantity and the second quantity. Pre-treating the carbon support caninclude removing impurities from the carbon support. Pre-treating thecarbon support can include mixing a third quantity of the carbon supportwith a first volume of hydrochloric acid. The third quantity can includeabout 0.2 grams (g) of the carbon support. The first volume can includeabout 40 milliliters (mL). The hydrochloric acid can have a molarity ofabout 0.5 moles (M). The third quantity can be mixed with the firstvolume for a duration at a rotational speed. The duration can be about15 hours. The rotational speed can be about 400 rotations per minute(rpm). Mixing the first quantity of tungsten salt and the secondquantity of nickel salt can include selecting the first quantity and thesecond quantity such that a molar ratio of tungsten salt to nickel saltis about 1:1. The molar ratio of tungsten to nickel can be about 3:1.The first quantity of tungsten salt can consist of WCl₆ and the secondquantity of nickel salt can consist of Ni(NO₃)₂.6H₂O. The molar ratio oftungsten to nickel can be about 4:1 or 5:1. Mixing the first quantity oftungsten salt and the second quantity of nickel salt on the carbonsupport can include several steps. A fourth quantity of the carbonsupport can be dispersed in a second volume of de-ionized water to forma carbon slurry. The first quantity of tungsten salt can be dissolved ina third volume of isopropanol. The dissolved first quantity of tungstensalt in the third volume of isopropanol can be added to the carbonslurry. A fourth volume of de-ionized water can be added to the mixtureof the tungsten salt in the carbon slurry. A mixture of the fourthvolume of de-ionized water and the mixture of the tungsten salt in thecarbon slurry can be stirred for a duration. The mixture of the fourthvolume of the de-ionized water and the mixture of the tungsten salt inthe carbon slurry can be vacuum dried after the duration. After removingthe water and the adsorbed oxygen, flowing the methane gas over themixture of the first quantity and the second quantity can includeincreasing a temperature of the mixture to about 1000° C. Thetemperature can be increased at a rate of about 5 degree Centigrade perminute (° C./min). The temperature of the mixture can be held for arespective duration at each of about 700° C., about 800° C., about 900°C. and about 1000° C. The carbon support can be conductive andhydrophobic. After removing the water and adsorbed oxygen and flowingthe methane gas over the mixture of the first quantity and the secondquantity, the mixture can be used as an electrode material, for example,as a catalyst, for hydrogen generation from brine by electrolysis. Themixture of the first quantity and the second quantity can be anickel-tungsten carbide alloy. A surface area of the carbon support canrange between about 50 square meters per gram (m²/g) to about 3000 m²/g.

Some aspects of the subject matter described here can be implemented asan electrode material for electrolytic hydrogen generation from brineincluding tungsten-nickel carbide (W—Ni—C) on a carbon support. Thetungsten-nickel carbide has a molar ratio of tungsten to nickel ofbetween 1:1 and 5:1.

This, and other aspects, can include one or more of the followingfeatures. The molar ratio can be about 1:1, about 2:1, about 3:1, about4:1 or about 5:1. The carbon support can have a surface area between 50m²/g to about 3000 m²/g. The tungsten-nickel carbides on the carbonsupports can have a particle size ranging between about 10 nanometers(nm) and 100 nm. The electrode material can be formed by mixing a firstquantity of tungsten (W) salt and a second quantity of nickel (Ni) saltin the presence of a carbon support and flowing methane gas over themixture of the first quantity and the second quantity to formtungsten-nickel carbides (W—Ni—C) on said carbon support. The firstquantity of tungsten salt can consist of WCl₆ and the second quantity ofnickel salt can consist of Ni(NO₃)₂.6H₂O. The mixture can have water andoxygen removed prior to flowing methane gas over the mixture. Thetungsten salt can be dissolved in isopropanol and the nickel salt can beprovided on the carbon support. The methane gas flowing over the mixturecan increase a temperature of the mixture to about 1000° C.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description later. Other features, aspects, andadvantages of the subject matter will become apparent from thedescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of an example process for producing electrodematerials.

FIG. 2 shows a schematic diagram of an example system for producingelectrode materials.

FIG. 3A shows Hydrogen Evolution Reaction (HER) Polarization curves inW—Ni—C/Vu (1:1) at different heat treatment temperature.

FIG. 3B shows HER Polarization curves in Vulcan carbon (Vu), Ni/Vu,W/Vu, W—Ni—C/Vu (1:1) and Pt/C respectively.

FIG. 3C shows HER Polarization curves in W—Ni—C/Vu at different moleratio of Ni:W.

FIG. 4A shows polarization curves of W—Ni—C/Vu (4:1) in N₂ saturated 0.5M NaBr, pH˜7.04 with consecutive cyclic volt-ammograms recorded,potential scan rate of 50 mV/s.

FIG. 4B shows polarization curves of W—Ni—C/Vu (4:1) in N₂ saturated 0.5M NaBr, pH˜7.04 before and after 1000 potential sweeps (−0.45 to +0.75V/RHE), potential scan rate of 20 mV/S.

FIG. 4C shows chrono-amperometry curves of W—Ni—C/Vu (4:1) in N₂saturated 0.5 M NaBr, pH˜7.04 at −0.37 V/RHE.

FIGS. 5A-5D show Scanning Electron Microscope (SEM) images of electrodematerials of different Ni:W molar ratios.

FIGS. 6A-6D show X-Ray diffraction patterns of synthesized catalysts atdifferent mole ratios atomic of Ni to W.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Electrolytic or photo-catalytic hydrogen production (or both) from brinewater can be an improvement relative to other industrial hydrogenproduction techniques, for example, in terms of cost and environmentalimpact. Such hydrogen production techniques use energy that is highenough to dissociate water molecules and release hydrogen. The type ofsurface on which the dissociation occurs affects significantly thequantity of energy used. Also, energy cost can be affected by using acatalyst that can lower the over voltage of the electrolytic process toproduce hydrogen from brine.

Precious metals, for example, platinum (Pt), which are used as catalystsin electrolysis, offer low over potential and faster reaction kineticsfor hydrogen evolution reaction (HER). However, such metals,particularly Pt, can be expensive and, consequently, prohibitive forapplication for hydrogen production from brine on an industrial scale.For example, it is known that coating Pt on Tungsten Carbide (WC), forexample, by atomic layer deposition or physical vapor deposition, canreduce Pt loading, but is a complicated process that is difficult to bescaled up to industrial levels.

This disclosure describes electrolytic hydrogen generation and anelectrode material for electrolytic hydrogen generation. The electrodematerial described here can be implemented as an efficientelectro-catalyst for hydrogen generation from brine, for example, atindustrial levels. As described later, the electrode material isprepared from materials that are abundantly available on earth. Theelectrode material described here shows significant reduction inover-potential for HER in brine electrolysis. The resulting electrodematerial can be based on a nano-structured electro-active material andcan be implemented as a catalyst in brine electrolysis and can serve asa cost-effective, stable and active alternative to expensive, preciousmetals, for example, Pt.

In some implementations, the electrode material can includetungsten-nickel based carbides, for example, W_(x)—Ni_(y)—C, WC, W₂C, orother tungsten-nickel based carbides, prepared by effectivelycontrolling the synthesis temperature and composition. As describedlater, such mixtures have shown excellent electro-activeness towardhydrogen evolution reaction from brine with an electrode performanceclose to that of Pt-based catalysts.

FIG. 1 is a flowchart of an example process 200 for producing electrodematerials. In some implementations, the process 100 can be implementedusing the system 100. At 102, tungsten (W) salt is mixed with nickel(Ni) salt on a carbon support. For example, WCl₆, is mixed withNi(NO₃)₂.6H₂O on a carbon support, for example, a conductive andhydrophobic carbon support, such as Vulcan XC-72R in a container 102. Insome implementations, a surface area of the carbon support can rangebetween about 50 m²/g to about 3000 m²/g. At 104, water and adsorbedoxygen are removed from the mixture prior to heating at differenttemperatures, for example, 700° C., 800° C., 900° C., 1000° C. or othertemperatures. For example, the mixture resulting by implementing step102 can be kept in a container 104 having an inert atmosphere, forexample, N₂ atmosphere. Then, at 106, low flow of CH₄ gas, for example,from a CH₄ gas source 106, can be passed over the mixture to form thecarbides at higher temperature, >700° C. For example, the methane gascan be flowed at a low flow rate, for example, 100 milliliters perminute (mL/min) for a reactor of about 5 centimeter (cm) diameter. At108, a carbide composite having a specified mole ratio can besynthesized. For example, the mole ratios of Ni to W can be about 1:1,1:3, 1:4, 1:5 or other mole ratios. In general, the tungsten-nickelcarbides can be represented as W_(x)—Ni_(y) in carbide form with x beingabout 50% to 75% atomic and y being about 50% to 25% atomic. In someexamples, x can range between 75% and 80%, and y can range between 20%and 25%. In some implementations, the carbide composites can becharacterized and also prepared in the form of electrodes, and testedfor HER in brine medium using a two or three-electrode electrolytic cellimplementation. Experiments described later are performed on alaboratory-scale, but can be scaled up to industrial levels to producelarge quantities of the electrode materials.

Experiment I—Pre-Treatment of Carbon Support

FIG. 2 shows a schematic diagram of an example system for producingelectrode materials. Initially, Vulcan XC-72R carbon support waspre-treated to remove traces of any impurities, such as metals. In acontainer 202, a quantity of 0.2 g of the Vulcan XC-72R was mixed in 40mL of 0.5 M hydrochloric acid (HCl) for a duration of approximately 15hrs at moderate temperature (20° C.-40° C.), while stirring at 400 rpm,for example, using a magnetic stirrer. The quantity of carbon support,for example, Vulcan XC-72R, ranged from 0.3 g to 0.4 g duringpre-treatment in acid. In general, a quantity of carbon support used candepend on an amount of electrode material, for example, catalyst, to beproduced. After carbon cleaning, for example, by the pre-treatmentdescribed here, in acid to remove traces of impurities, for example,metals or other impurities, 0.2 g of treated carbon was used to developthe carbide materials on the carbon surface. The amount of carbon usedcan be more than the amount of carbon needed to account for carbon loss.The carbon support was then filtered, washed and dried in an oven 204 at80° C. for 6-7 hrs.

Experiment II—Preparation of Electrode Material Having Ni:W in a 1:1Ratio

To prepare the electrode material, 0.2 g of Vulcan carbon, pre-treatedas described earlier, was dispersed in a container 206 containing 40 mLde-ionized water by sonication for 20-30 minutes, and then transferredto a glass beaker 208 with magnetic stirrer 210 (rotated by a stir plate212) to form a carbon slurry. Thereafter, 0.4 g of WCl₆ dissolved in acontainer 212 containing 30 mL isopropanol (IPA) was slowly added to thecarbon slurry. To maintain an atomic ratio of Ni:W or 1:1, 0.29 g ofNi(NO₃)₂.6H₂O was dissolved in a container 214 containing 20 mL ofde-ionized H₂O and added, drop-wise, to the mixture in the container208, followed by a final rinse with 10 mL of de-ionized H₂O to make-up100 mL of reaction volume. The mixture was left under stirring at 500rpm for 2-3 days for proper impregnation of metal salts onto the carbonmatrix. The mixture was then vacuum-dried at 80° C. between 6 and 7 hrsin an oven 216.

The resulting sample was heat-treated as follows. The powdered samplewas placed in a crucible boat and transferred into a quartz tube MTIfurnace 218 (OTF-1200X-S). Gas cylinders were connected to the gas inletof the furnace and the exhaust/outlet was directed to an oil bath.Nitrogen (N₂) gas was first passed into the furnace while thetemperature was first increased from room temperature to 100° C. for 30minutes and held at this temperature for 10 minutes to purge outadsorbed oxygen and water. Methane (CH₄) gas flow was then passed whileramping temperature of the furnace at a rate of 5° C./min to the desiredtemperatures of 700° C., 800° C., 900° C. or 1000° C., and held for 1hr. In general, a quality of the sample is affected by a ramping period,that is, the time to reach a set temperature value at which catalystformation begins and a temperature hold period, that is, the time forwhich the temperature is held for catalyst active sites formation.

Subsequently, some of the samples synthesized at Ni:W ratio of 1:1 werecooled and used to study the effect of temperature on HER performance,as described later. In some implementations, the samples can be cooledat any rate. For example, the cooling can be done under ambientconditions without an external cooling system. In some implementations,external cooling systems can be used to cool the samples at coolingrates ranging between about 5° C./min and 10° C./min. In someimplementations, the cooling can be implemented by simply turning offthe heating chamber in which the samples are heated. Cooling can be doneunder the flow of methane or an inert gas to avoid leak of oxygen intoreactor.

Experiment III-V—Preparation of Electrode Material Having Ni:W in a 1:3,1:4 and 1:5 Ratio, Respectively

To prepare the electrode material having Ni:W in ratios of 1:3, 1:4 and1:5, 1.2 g, 1.6 g and 2.0 g of WCl₆, respectively, was mixed with 0.29 gof Vulcan carbon, pre-treated as described earlier. The electrodematerial in each of these ratios was prepared by processing each mixturein a manner similar to that described earlier. Each obtained sample wascharacterized using a thin film electrode in a three-electrode geometriccell and also by spectroscopic techniques to investigate themorphological structure and composition of each sample.

For each sample prepared as described later, HER activity in brine werestudied, as described later.

Experiment VI—Studying HER Activity in Brine

For each sample prepared as described earlier, approximately 5 mg of thesample was dispersed in a mixture of water and isopropanol (30% V/V) and37 μL of 1.66% wt Nafion® (prepared from 5% wt). The mixture wassonicated to obtain a uniform ink. The working electrode used duringelectrolysis was prepared by depositing 16 μL of the ink suspension onthe pre-cleaned glassy carbon substrate and allowed to dry under airflow at room temperature. The loading operation was repeated until thedesired catalyst loading, 0.4 mg/cm² was achieved and the geometric areaof the glassy carbon rotating disk electrode (RDE) was about 0.196 cm².A Pt mesh was used as a counter electrode during activity measurementsin brine (0.5 M NaBr, pH˜7.04, specific gravity˜1.54). A Calomelelectrode (calibrated against reversible hydrogen electrode every dayprior to activity measurement of HER) was used as a reference electrode.All potential measurements during these studies were converted toreversible hydrogen electrode (RHE).

Results—HER Activity in Brine

FIG. 3A shows HER polarization curves for Ni:W in a mole ratio of 1:1 atdifferent heat treatment temperatures in the presence of methane gasflow. The polarization curves show that sample treated at 800° C. showsbetter HER activity than the other samples with an over-voltage of 300millivolt (mV) as compared to Pt/C catalyst. This can indicate thatformation of more active sites for HER for the specific composite ismore favorable at this temperature.

FIG. 3B shows HER polarization curves obtained for individual metalcarbides. Vulcan carbon shows the highest over potential for HER. WC/Vubehaves better than its homologue, NiC/C. A significant improvement inHER activity is observed when both metals are incorporated at 1:1 moleratio of Ni:W.

FIG. 3C shows HER polarization curves in brine for the carbidecomposites including two metals. The polarization curves were generatedto study if the electro-catalytic synergistic effect of the two metalsincreased the HER performance of the carbide composite. An increase incurrent density and a reduction in over-potential were observed with HERactivity close to that of bulk Pt/C. When the mole ratio of Ni:W wasoptimized from 1:1 to 1:4, a corresponding reduction in over potentialwas significant. However, when the ratio is 1:5, a drastic reduction inactivity of the catalyst toward HER in brine was noticed suggesting thatthe best molar ratio of Ni:W to lead to metal carbide alloys aspotential Pt-free electro-catalyst for HER is 1:4. Such enhancement inHER activity may be due to effective utilization of the synergisticeffect of the two metals that favor faster HER kinetics.

Experiment and Results—Catalyst Stability

For stability studies, the catalyst that demonstrated highest HERactivity, that is, Ni:W in a molar ratio of 1:4 (for example, W—Ni—C/Vuin a 4:1 ratio), was used. To investigate the long term performance forthe catalyst in brine, potential sweeps were conducted from −0.45 to+0.75V/RHE for 1000 cycles as shown in FIG. 4A. FIG. 4B shows thepolarization curve recorded before and after the stability test. Thecatalyst demonstrated good stability by maintaining almost its initialpolarization behavior in brine medium. To further establish the catalyststability, chrono-amperometry (CA) studies was also conducted at apotential hold of −0.37 V/RHE (corresponding to j=1 mA cm⁻²) for 1 hr asshown in FIG. 4C.

Scanning Electron Microscope (SEM) Images and X-Ray Diffraction

FIGS. 5A-5D are Scanning Electron Microscope (SEM) images of electrodematerials of different Ni:W molar ratios. FIG. 5A is the SEM image ofthe composition having W:Ni in a 1:1 ratio. FIG. 5B is the SEM image ofthe composition having W:Ni in a 3:1 ratio. FIG. 5C is the SEM image ofthe composition having W:Ni in a 4:1 ratio. FIG. 5D is the SEM image ofthe composition having W:Ni in a 5:1 ratio. The composite with molarratio of W:Ni of 5 to 1 (FIG. 5D) appears to be more dense than thosecorresponding to ratios, 4:1, 3:1, and 1:1. The difference in densitymay be the reason that HER activity was decreased significantly for thiscomposition relative to the other compositions.

FIGS. 6A-6D show X-Ray diffraction patterns of synthesized catalysts atdifferent mole ratios atomic of Ni to W. FIG. 6A is an XRD pattern ofcatalyst having W:Ni in a 1:1 ratio. FIG. 6B is an XRD pattern ofcatalyst having W:Ni in a 3:1 ratio. FIG. 6C is an XRD pattern ofcatalyst having W:Ni in a 4:1 ratio. FIG. 6A is an XRD pattern ofcatalyst having W:Ni in a 5:1 ratio. The XRD patterns of the synthesizedcatalysts show formations of mixture of metal carbides of tungsten metal(WC and W₂C) and W—Ni carbides alloys at different diffraction angles.The unassigned peak in the XRD figure corresponds to Carbon (002) plane.

In summary, the electrode material described here can serve as a costeffective and cheaper alloy material that can be used for hydrogenformation from brine through electrolysis. The alloy compositiondescribed here can allow hydrogen formation at high rates. The alloycomposition can replace relatively more expensive, precious metals, forexample, Pt.

Thus, particular implementations of the subject matter have beendescribed. Other implementations are within the scope of the followingclaims.

The invention claimed is:
 1. A method for forming an electrode for brineelectrolysis comprising: mixing a tungsten (W) salt with a nickel (Ni)salt on a carbon support to give a mixture; removing adsorbed oxygenfrom the mixture; flowing methane gas over the mixture and increasingtemperature of the mixture after removing adsorbed oxygen to formtungsten-nickel carbides (W—Ni—C) on the carbon support, wherein themolar ratio of tungsten to nickel is about 4:1; forming an inksuspension from the mixture on the carbon support by dispersing themixture in a water based solvent; depositing the ink suspension on aglassy carbon substrate; and drying the ink suspension on the glassycarbon substrate to form the electrode.
 2. The method of claim 1,comprising dissolving the tungsten salt in isopropanol.
 3. The method ofclaim 2, wherein the nickel salt is disposed on the carbon support, andwherein mixing the tungsten salt with the nickel salt comprises mixingthe tungsten salt dissolved in the isopropanol with the nickel salt asdisposed on the carbon support.
 4. The method of claim 1, wherein mixingthe tungsten (W) salt with the nickel salt (Ni) on the carbon supportcomprises: dissolving the tungsten salt in isopropanol; dispersing thenickel salt as disposed on the carbon support in water to form a carbonslurry; mixing the tungsten salt dissolved in the isopropanol with thecarbon slurry; and vacuum drying to give the mixture.
 5. The method ofclaim 1, wherein increasing the temperature comprises increasingtemperature of the mixture at a rate of at least 5° C. per minute. 6.The method of claim 1, wherein increasing temperature comprisesincreasing temperature of the mixture to at least 1000° C.
 7. The methodof claim 6, wherein increasing temperature comprises holding temperatureof the mixture at less than 1000° C. for a duration.
 8. The method ofclaim 1, comprising pre-treating the carbon support to remove impuritiesfrom the carbon support before mixing the tungsten salt with the nickelsalt.
 9. The method of claim 8, wherein pre-treating the carbon supportcomprises mixing the carbon support with an acid to form a slurry of thecarbon support in the acid, and filtering the carbon support from theslurry.
 10. The method of claim 9, wherein the acid compriseshydrochloric acid.
 11. The method claim 1, wherein the tungsten saltcomprises WCl₆ and the nickel salt comprises Ni(NO₃)₂ 6H₂O.
 12. Themethod of claim 1, wherein the carbon support is conductive andhydrophobic, wherein a surface area of the carbon support is in a rangeof about 50 square meters per gram (m²/g) to about 3000 m²/g, andwherein the tungsten-nickel carbides on the carbon support have aparticle size ranging between about 10 nanometers (nm) and 100 nm. 13.The method of claim 1, wherein flowing methane over the mixturecomprises flowing methane through the mixture producing thetungsten-nickel carbides as a nickel-tungsten carbide alloy.
 14. Themethod of claim 1, comprising generating hydrogen from brine byelectrolysis of the brine via electrode material, wherein the electrodematerial comprises the tungsten-nickel carbides on the carbon support.15. A method of electrolytic hydrogen generation, comprising generatinghydrogen from brine by electrolysis of the brine via an electrodecomprising an electrode material, wherein the electrode materialcomprises a tungsten-nickel carbide on a carbon support, wherein themolar ratio of tungsten to nickel is about 4:1, wherein the electrode isformed by: dispersing the electrode material in a water based solvent toform an ink suspension; depositing the ink suspension on a glassy carbonsubstrate; and drying the ink suspension on the glassy carbon substrateto form the electrode.
 16. The method of claim 15, wherein thetungsten-nickel carbide comprises a tungsten-nickel carbide alloy. 17.The method of claim 15, wherein the tungsten-nickel carbide on thecarbon support has a particle size in a range of 10 nanometers (nm) to100 nm, wherein the carbon support is conductive and hydrophobic, andwherein the carbon support comprises a surface area in a range of 50square meters per gram (m²/g) to 3000 m²/g.
 18. The method of claim 15,wherein the tungsten-nickel carbide on the carbon support is formed byremoving adsorbed oxygen from a mixture of a tungsten salt and a nickelsalt on the carbon support and subsequently flowing methane over themixture.